Building on the progress in the current grant, the proposed research will address outstanding questions regarding glottal aerodynamics, focusing on the contribution of the glottal jet to (1) glottal impedance, (2) aeroacoustic sources in phonation, and (3) energy losses that limit voice efficiency, and how these are quantified by aerodynamic and acoustic measures currently available in clinical practice. A coordinated study comprising physical model experiments, computation, and theoretical modeling will address these issues for vibration of biomechanically symmetric and asymmetric model vocal folds. In the experimental studies, temporally and spatially resolved measurements of flow velocity and the vocal fold wall position will be performed using Digital Particle Image Velocimetry in a scaled-up model of the vocal folds. Other experiments will use a life-scale model using self-oscillating model vocal folds, and will additionally include measurements of acoustic and aerodynamic pressure, and oral volume flow using a pneumotach. Computer simulations will study both driven and self-oscillating model vocal fold walls. For all cases studied, glottal volume flow, the aeroacoustic sources, and the aerodynamic losses will be characterized in terms of the glottal jet structure (vortex shedding, flow asymmetry, jet impedance). The experiments and model development will build on previous work of the investigators, combining expertise in experimental and computational fluid mechanics, aeroacoustics, flow-induced vibration, and the application of these to phonation. Participation of a consultant voice researcher/surgeon will also help keep the proposed research focused on clinical relevance. PUBLIC HEALTH RELEVANCE: This research will address the underlying physical mechanisms that cause voice production. This knowledge will assist physicians in choosing alternative treatments of voice disorders, and will be used to better interpret clinical measures of voice function in current use.